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CE-2 flyby of Toutatis
Explorer1
post Dec 15 2012, 12:06 AM
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Very fast release! I'm glad to have been wrong in my earlier speculation. I wonder how real/fake the color is.
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elakdawalla
post Dec 15 2012, 12:09 AM
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I wonder, were these images taken with the webcam-style cameras they used to monitor deployments and rocket firings?


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Phil Stooke
post Dec 15 2012, 12:18 AM
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3.2 km? Amazing, just amazing. Solar panel monitoring camera power up... I guess it was that one. Does this mean there's more to come from the main camera?

Phil


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mcaplinger
post Dec 15 2012, 12:28 AM
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QUOTE (Phil Stooke @ Dec 14 2012, 05:18 PM) *
3.2 km? Amazing, just amazing.

Can that be right? Navigationally I'd have thought getting that close was impossible without some kind of autonomous or at least very fast-turn optical navigation. Impressive if true.


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elakdawalla
post Dec 15 2012, 12:38 AM
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I'm trying to figure out what the scale of the image is, with the endgame, of course, being the addition of this body to my asteroids-visited-by-spacecraft montage. A major question for an elongated body is: are we seeing its maximum dimension, or is it foreshortened?

From this JPL page, the radar-derived dimensions of Toutatis:
"The asteroid's maximum extents along the principal axes are (1.92, 2.29, 4.60) +/- 0.10 km. "

Measuring on the photo, I get that the long axis here (which may not be the full length, if it's not broadside-on) is 792 pix
The short axis here should be somewhere in between the 1.92 and 2.29 axes, and it's 312 pix

That ratio is about 0.4, which is almost identical to 1.92/4.60

Which would mean that (assuming the JPL numbers are correct) we really are looking at it pretty close to broadside-on, with the plane of the sky being close to the plane of the minimum and maximum principal axes.

Somebody please check my work!!


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machi
post Dec 15 2012, 12:59 AM
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My measurements are: long axis ~800 pix, short axis ~330 pix and ratio 0.4125.


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Phil Stooke
post Dec 15 2012, 01:06 AM
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I can confirm that this view shows the long dimension, probably no more than a little bit foreshortened. I think it's pretty much being viewed along its shortest axis, so we are seeing the long and intermediate axes.

Phil


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Phil Stooke
post Dec 15 2012, 01:26 AM
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Bringing out a bit more detail in the brighter areas:

Attached Image


(Thanks, Chinese space agency, for these great pictures)

Phil


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machi
post Dec 15 2012, 01:46 AM
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Attempted comparison with Goldstone radar imagery.
Attached thumbnail(s)
Attached Image
 


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ElkGroveDan
post Dec 15 2012, 02:37 AM
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Is there any doubt that we are looking at two distinctly separate objects in contact?


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Phil Stooke
post Dec 15 2012, 02:47 AM
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If this is an approach sequence, there may be a departure sequence as well.

Phil



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elakdawalla
post Dec 15 2012, 02:58 AM
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Beginning to look at the image and try some early (read: arm-waving) interpretation. Some things I notice: there are boulders that remind me of Itokawa. But they're sparse; it's substantially smoother than Itokawa. So I'd interpret that to mean it is mostly covered in a regolith. I also see circular depressions of a wide variety of sizes, the sort of thing one would tend to interpret as impact craters. Some have sharper edges than others. Of course, you have to be cautious; smaller ones especially might be collapse pits. I'm intrigued by the apparent roughness of the larger end. Again, though, I need to be careful; its apparent roughness could be due to lighting geometry. It's a pretty low-phase-angle image. Overall, it seems faceted. A slope map of this thing would be fascinating.


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yaohua2000
post Dec 15 2012, 03:01 AM
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More info: 20 Kbps at 7 million km, 90% data has been received so far.

This is a television screenshot of a close-up image at 5 m/pixel, captured at 08:30:05, 47 km away. (Hope to have raw image soon)
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tedstryk
post Dec 15 2012, 03:07 AM
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Thanks for posting that! I think you mean 5 m/pixel.


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Phil Stooke
post Dec 15 2012, 04:30 AM
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Shape model and slope map here:

http://echo.jpl.nasa.gov/asteroids/4179_Toutatis/hires.pdf

Phil



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